1. Field of the Invention
The present invention relates to a thermodynamic apparatus and a method for the absorption and emission of heat, wherein at least one temperature during heat emission is located above at least one temperature during heat absorption.
2. Prior Art
One conventional technology for the production of cooling energy in air-conditioning and for cooling purposes are mechanically driven compression cooling devices. As an alternative, also absorption refrigeration devices with conventional tube bundle or plate absorbers are used. Recently, also adsorption cooling devices are developed based on zeolites, with a similar working process like absorption refrigeration devices.
Refrigeration devices have the task to absorb heat at low temperatures and to emit heat at high temperatures again. The profit is the absorption of heat at low temperature. The same process is performed by heating pumps; however, here the profit comes from the heat emission at high temperature. There are further modifications like heat transformers, where the heat is absorbed at medium temperature and emitted at high (useful heat) and at very low (waste heat) temperature.
The process of the aforemntioned kind will be described here for a refrigeration device as an example. It can be applied accordingly to the other mentioned processes heat pump and heat transformer.
Adsorption, absorption and compression cooling devices need an evaporator, which absorbs the heat from the object to be cooled during an evaporation at low temperature and low pressure and a condenser in which the cooling agent condensates after being compressed to higher pressure at environmental temperature level under heat emission to the environment. While in a compression cooling device the gas compressor compresses the cooling agent vapor to the pressure required for condensation, in an absorption or adsorption refrigeration device this function is performed by a so called “thermal compressor”. This is a solvent cycle with cooled adsorber or absorber and heated desorber. The absorber in which the cooling agent vapor is absorbed at low pressure from the solvent operates on a similar temperature level as the condenser. In the desorber, the cooling agent will be emitted again by heat addition from the solvent at high temperature under high pressure. In case of a volatile solvent, a rectification is needed for the desorber, in order to obtain pure cooling agent vapor.
Absorption refrigeration devices, as well as compression cooling devices, are sensible to mechanical shocks. In addition adsorption and absorption refrigeration devices require higher investment costs and show up a bigger construction volume and a higher weight than compression cooling devices.
When in an absorption refrigerator a volatile solvent such as water is used, the required rectification increases the investment costs and the construction volume further. Most of the investment costs of an absorption refrigerator are attributed to the heat transmitters. The absorber—with a part of about 40%—contributes the most to the total installed heating transmitter surface.
Because of their lack of mechanical robustness nowadays absorption refrigeration devices cannot be used in mobile sectors. This lack of mechanical robustness is related to the fact that in devices with liquid films, the liquid wetting of the heat exchanger surface are negatively affected by mechanical shocks, because the liquid gets through the devices as a free falling film.
In adsorption refrigeration devices, the main problem is the low heat transfer in the adsorber and desorber, as in these devices, no liquid is included and therefore, only the mechanisms of the heat conduction in fixed beds and the gas flow are relevant for the heat transport This causes increased investment costs compared to an absorption refrigerator.
Too high investment costs and too big construction volume are main obstacles which obstruct a further spreading of the absorption refrigeration technology and lead to the fact, that even in case that cheap energy is available—like waste heat—compression cooling devices are often preferred with the main disadvantage of consuming high quality mechanical energy.
From the German patent specification 633 146, an absorption device—especially a continuously working absorption refrigerator—is known, in which the solution coming from a boiler/evaporator gets into an storage tank, then flowing into a liquid filled absorber equipped with a diaphragm Here gas is absorbed through its diaphragmatic wall. With this construction the danger of a change in flow direction of the liquid can be eliminated without requiring a pump. This device described in DE-PS 633 146 is a precursor of today's membrane/diaphragm-less absorption diffusion refrigerator.
DE 195 11 709 A1 reveals a sorption refrigerator in which the solvent that is at the same time the cooling medium is flowing in a circuit in a mixture with a sorption medium and is transferred by pervaporation from a highly concentrated to a low-concentration solution. In order to enable a transport contrarily to the concentration gradient, a temperature difference must be guaranteed in the device by simultaneous heating of the concentrated solution and cooling of the lean solution (reverse osmosis principle). Here, both solutions are separated inside the device by means of a semipermeable membrane. In addition conventional Desorber and absorber are used.
Based on this the invention has the object to eliminate the disadvantages of conventional processes by providing a refrigeration device/method or heat pump process which is cheap, compact and mechanical shock resistant.